Cancer metastasis is determined by the biological nature of cancer. Cancer cells have the characteristic of unlimited proliferation and may infiltrate into the surrounding and metastasize to distant places, mainly through direct spread, lymphatic channel and blood line metastasis. 1. Lymphatic metastasis: usually, cancer cells can be shed and invade into lymphatic vessels, and with the lymphatic fluid, they can reach local lymph nodes and form metastatic cancer in lymph nodes. Multiple metastatic lymph nodes can merge with each other to form a lymph node mass, and after localized lymph node metastasis, the metastasis can continue to develop to the next station of lymph nodes. Cancer cells can enter the blood stream through thoracic duct and then metastasize to the blood tract. 2、Bloodway metastasis: tumor cells first invade the basement membrane and infiltrate in the surrounding mesenchyme, then pass through the interstitial space of vascular endothelial cells and form tumor embolus in the blood vessel, and then the dislodged tumor cell embolus, run along the direction of venous system. The most likely sites of hematogenous metastasis are liver and lung. 3、Growth metastasis: it is a form of tumor cell metastasis generated in mucosa, plasma membrane or other places. Plasma membrane surface metastasis is common in peritoneum and pleura, followed by subarachnoid space, pericardium and rarely testicular sheath. When the tumor cells penetrate the plasma membrane of the above organs, the cancer cells can be detached, and like sowing seeds, the tumor cells are scattered on the surface of the plasma membrane, forming corn-grain nodules of varying sizes, and some nodules can be fused to form a pie shape. Cancer patients can only reduce the incidence of metastasis by early detection, early diagnosis and timely treatment.